In general, a customer receives supply of power from a transmission line or distribution line from an electric supply company based on a contract made in advance with the electric supply company and guides power to the local cable of the customer to supply power to electric appliances from an outlet. The outlet is installed inside of the customer or the site.
Ordinarily, power supplied to the outlet from the electric supply company is supplied from the local cable via the distribution line, but, there is a case where power is supplied directly from the transmission line or distribution line, and therefore, in the following explanation, the outlet to which power is supplied from the distribution line includes an outlet to which power is supplied directly from the transmission line or distribution line and an outlet to which power is supplied from the local cable.
As described above, a customer connects plugs of various kinds of electric appliances into the outlet to which power is supplied from the distribution line and uses the electric appliances. In this manner, ordinarily, power is used via the outlet in the customer site.
On the other hand, when the contracted power is determined based on the contract made with the electric supply company, a breaker having a current limit value in correspondence to the contracted power is installed in the customer and the maximum current that can be used in the customer is suppressed to within the current limit value determined by the breaker.
There is a system in which a home server is installed in a customer site to make it possible to check the power supply state for electric appliances connected to a plurality of outlets of a table tap in the house or to switch the power supply state to another if necessary by transmitting a control signal to the home server from a push telephone while leaving home (for example, see PLT 1).